1. Field of the Invention
The present invention relates to a fail detecting device for a rotation angle sensor. More particularly to a fail detecting device for a rotation angle sensor for detecting the fail state of the rotation angle sensor that detects the rotation angle of an object to be detected.
2. Description of Background Art
Conventionally, there has been known a configuration in which a plurality of rotation angle sensors are provided in a rotation angle detecting system to detect the rotation angle of a rotating body as preparation for the occurrence of a fail such as breakdown in the rotation angle sensor.
Japanese Patent Laid-open No. 2005-265768 discloses a configuration in a rotation angle detecting system to detect the rotation angle of a ball bearing configured with a bearing ring composed of inner ring and outer ring. A plurality of spherical rolling elements rotate along the bearing ring with a cage that separates the rolling elements. More specifically, in this configuration, at least two rotation angle sensors formed of Hall elements are provided to detect the rotation angle of the cage.
However, in the technique described in Japanese Patent Laid-open No. 2005-265768, although a fail can be easily detected by comparing the respective sensor outputs even when a fail such as breakdown has occurred in any sensor, there is a problem that the increase in the number of sensors causes an increase in the number of parts and an increase in the complexity of arithmetic processing, and so forth.